If I'm being honest, I can't afford insurance on both at the same time. Both are currently insured, but the GTI basically has 'storage' coverage for the time being. To swap between the two, I think my insurer needs 30ish days to flip-flop the coverage. So to answer your question, 0 miles on the GTI since I picked up the R. I've moved it a few times to clean it, and getting in/driving around the block reminds me that it's such a different driving experience than the R (in a good way). Can't part with it.
Currently, I think I'm going to swap back to the GTI for one more winter and go from there. The idea was to go 6 months R : 6 months GTI, just can't decide yet on which car gets winter.
HVAC on the GTI is on it's way out the door, so mid winter and mid summer both suck ass in it. I can handle it, but I do most of the driving and my partner isn't a fan. (she loves the R even moreso for that reason).
Big first world problems, basically a dream come true so feeling humble.